1. Field of the Invention
The present general inventive concept disclosed herein relates to a semiconductor memory device, and more particularly, to a memory system including nonvolatile memory device and an operating method thereof.
2. Description of the Related Art
A semiconductor memory device is a micro electronic device most necessary for digital logic designs that include computers that have a microprocessor, with applications ranging from satellites to consumer electronic technologies. A semiconductor memory device is largely divided into a volatile semiconductor memory device and a nonvolatile semiconductor memory device. The nonvolatile semiconductor memory device may store data even when a power source is shut off. Data stored in nonvolatile memories may be semipermanent or reprogrammed according to memory manufacturing technologies. The nonvolatile semiconductor memory device is used for storing programs and micro codes in a wide range of applications such as computers, avionics, communication, and consumer electronic technologies.
As a representative example of a nonvolatile memory device, there is a flash memory device. Recently, as the high integration of memory devices is increasingly required, multi-bit memory devices are being generalized which store multi-bits in one memory cell. In the memory cells of a multi-bit flash memory device, the interval between threshold voltage distributions should be densely controlled. Also, technologies are being researched for improving a degree of integration for increasing the number of memory cells per unit area in order to meet high-capacity requirements.